Journal of Machinery Manufacture and Reliability最新文献

A numerical analysis of the influence of a corrective function on the calculated durability is presented. The boundaries of variation of arguments have been formed: the limits of endurance and maximum stress amplitudes of the destructive load block. Paradoxical results presented in the graphs were obtained under the boundary conditions provided in the references.

This article discusses the features of using elastic bush–pin couplings. Calculation and selection of fits is presented for the case of using elastic bush–pin coupling halves of different designs with different diameters of landing holes. The connection between the shaft of an A280S8 electric motor and the shaft of the WVP’1-25 vacuum pump with an elastic sleeve-pin coupling was chosen as the object of research. It has been found that the electric motor shaft connection with a (emptyset )80 mm coupling during assembly using the pressing-in method should be assigned an H8/t6 fit, and when heating the coupling, H8/t7. To connect the shaft of WVP’1-25 vacuum pump with a coupling of (emptyset )65 mm, for any type of assembly, one can assign an H8/t6 fit, in which the maximum tension is four microns higher than the maximum established limit of technological tension, which can lead to destruction of the cast iron coupling. In this regard, it is recommended to the coupling manufacturer to increase the equipment accuracy in order to provide a fit for the connection of the vacuum pump WVP’1-25 shaft with a coupling of (emptyset )65 mm in the form of H7/t6, which will meet the calculated accuracy requirements.

Increasing the efficiency of using explosion energy to destroy a rock massif when operating solid-fuel shock wave generators, which include an explosion-reactive system, depends, to a considerable extent on the parameters of the pressure impulse, on the physical and mechanical properties of the rocks, and on the mining and geological conditions. Simulation results for the parameters of an explosion impulse during the operation of an explosion-reactive system are presented, and pressure impulse amplitudes under different pulse duration modes are studied. A rational mode of operation of the explosive system is determined for the development of rocks with strength coefficient f = 5–20 according to Profesor Protod’yakonov’s scale has been determined.

The influence of electric current pulses passing between parts during fretting wear of titanium alloys is examined. A description of the test bench and a description of the test methodology are given.

The sealing cup selection procedure for shaft surfaces during repairs is substantiated theoretically and tested practically. The procedure consists of justifying the diameters of the repair dimensions of the shafts based on wear data and selecting sealing cups for these dimensions according to the internal diameter in order to ensure the same tightness as for new connections. The practical application of the procedure is considered on a transmission output shaft connection.

The problem of automation intended for the analysis and synthesis of deployable parabolic antennas is considered. The interrelated variable parameters of the mating elements of a deployable parabolic reflector of an antenna with an axisymmetric packaging of the petals and spherical mechanisms for their deployment in the form of conical gear pairs have been chosen and studied. A comparative analysis of the variants of petal deployment mechanisms with constant and variable gear ratios has been conducted.

Currently, variable compression ratio engines are not used, presumably due to the complexity of the design. Currently, various engines are being developed that differ in design, kinematics, load control and compression ratio changes. The article presents the results of calculating the efficiency and fuel consumption for a crankshaft with a rotation speed of 2000 and 4000 rpm with a compression ratio of 8.6 and a rotation speed of 4000 rpm with a compression ratio of 13 and provides combustion characteristics m = 3 and 1. It is shown that these characteristics at higher speeds they approach the indicators at lower speeds with an increase in the compression ratio. The engine parameters were calculated for various modes based on Wiebe theory. Based on the calculations, the efficiency and fuel consumption are determined for the corresponding modes and the nature of the engine operation. It has been found that with an increase in the crankshaft rotation speed, the cycle efficiency will decrease by almost half and fuel consumption will increase accordingly; with an increase in the compression ratio, the efficiency is restored and fuel consumption decreases accordingly.

On the basis of experimental studies aimed at studying the phase composition of titanium powders obtained for additive machines by electrodispersion of OT4 alloy waste in propyl alcohol, the presence of the following phases in titanium powder particles was noted: α-Ti, TiO, and Ti₃Al. The studies carried out will make it possible to determine the most rational field of application of the obtained titanium powders for the production of additive products from them.

The results of an experimental study of a steam jet injector in the mode of generating nonlinear pressure oscillations of a relaxation nature are presented. High-frequency decaying pressure jumps were detected on the leading edge of the oscillation curve. It is shown that, when exciting oscillations, the injector operating mode changes from supersonic to subsonic. An explanation of the pressure oscillation process during the cycle is given. With a working steam pressure of 8–10 bar, an oscillation amplitude of 5–6 bar at frequencies of 5–20 Hz was obtained.

In this study, aluminum-based metal matrix composites (MMCs) were fabricated with varying compositions of SiC and TiO₂ reinforcements using the stir casting method. Three different compositions were examined: 98% Al6061 alloy, 1% SiC, and 1% TiO₂; 96% Al 6061 alloy, 2% SiC, and 2% TiO₂; and 94% Al alloy, 3% SiC, and 3% TiO₂. These MMCs were evaluated for their mechanical behavior and microstructure in terms of tensile, flexural, and impact strength. Scanning electron microscopy (SEM) analysis revealed a uniform distribution of reinforcements, while also indicating an uneven dispersion of SiC particles within the Al matrix. Tensile testing displayed an ultimate strength of 160.06 MPa, an elongation of 6.63%, and a hardness of 96.5 for the sample with the composition of 94% Al, 3% SiC, and 3% TiO₂. For the composition of 96% Al alloy, 2% SiC, and 2% TiO₂, the highest flexural strength of 6.57 kN, notable impact strength of 6 J, and a hardness value of 93.68 were achieved. Atomic force microscopy (AFM) was employed to analyze surface morphology. These results demonstrate the potential of these MMCs for practical applications due to their improved properties compared to commercially available composites. The study highlights the tailored mechanical attributes of metal matrix composites, showcasing their strength, stiffness, fatigue resistance, and corrosion resistance. Such systematic analyses aid in the development of more efficient and dependable structures for wind turbine applications.